Abstract: A relatively small liquid-crystal display (LCD) device located well above the fresnel stage of an overhead projector produces large, sharp images with full color and motion. A focus-correcting lens moves with the overhead projector's optical head to maintain proper projection-focus and magnification. Spectrally-selective filters are interposed between the LCD device and fresnel stage to avoid LCD deterioration. A fan-actuated shutter or electrically-actuated shutter optionally provide still further protection. Optical collimation methods are employed to attain a large depth-of-field and image brightness.

Abstract: An opaque adapter for an overhead projector uses a hood with clamshell doors to provide generous access to the projector stage during transparency projection and efficient light shielding during opaque projection. The clamshell doors are oriented upon hinges slanted to the vertical so as to rise away from the stage when opened. Spring devices offset the gravitational forces on the doors, allowing rapid motor actuation with very little power. Dual dichroic optics maintain a cool stage despite high light intensity, and internal baffles further increase brightness.

Abstract: An optical projector having opaque and transparency operating modes employs a pair of illumination paths, conventional overhead-projection optics, common focus elements, and a large-aperture stage. Oversized objects such as large books or magazines are accommodated by a resilient bottom of a light-constraining hood assembly. A light source is oriented in a manner that eliminates optical or physical interferences between the pair of projection modes. The hood assembly provides novel reflectivity for image intensification in the opaque mode and easy access to the stage for either opaque or transparency projection. Most elements associated with either projection mode can be detached in a unit, leaving solely the remaining mode capability.

Abstract: A compact, portable bar code scanner employing as a light source a light-emitting diode consumes extremely low input power. The scanner, which detects the reflectances from bars and spaces of the bar code symbol, uses optical beam-shaping methods to attain a large depth-of-focus for a non-laser system. A shaped illuminating light beam is caused to blink when the symbol is outside the depth-of-focus range and a signature imposed upon the light beam enables the scanner to substantially reject light interference. A scanning version employs an optical assembly mounted upon a bimorph leaf spring that is caused to vibrate at its natural mechanical resonance. The scanner operates with bar code symbols responsive to red light and is of sufficiently low weight to be easily hand-held.